forEach方法的实现

 var arr = [1, 23, 1, 1, 1, 3, 23, 5, 6, 7, 9, 9, 8, 5];
 Array.prototype.forEach = Array.prototype.forEach || function(callback, thisArg) {
         if (!callback || typeof callback !== 'function') return;
         for (var i = 0, j = this.length; i < j; i++) {
             callback.call(thisArg, this[i], i, this);
         }
 }

 /*
    forEach方法实现数组去重
 */

 var newArr = [];
 arr.forEach(function(ele,index,arr){
     if(arr.indexOf(ele)===index){
         newArr.push(ele);
     }
 })
 console.log(newArr);